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포타슘 술포네이트 폴리스타이렌 아이오노머의 기계적인 성질에 미치는 Crown ether의 영향
나연화,조규성,이법원,김준섭,유지강,박기주 조선대학교 생산기술연구소 1999 生産技術硏究 Vol.21 No.1
The effects of crown ether on the dynamic mechanical properties of potassium sulfonated polystyrene ionomer were investigated. As expected, it was found that when crown ether molecules were added to the ionomer, the crown ether molecules interacted with K^(+) cations and weakened the ionic interaction between K^(+)/sulfonate ion pairs of the ionomer significantly. Thus, no multiplets were present, and, in turn, no clustering was found. When the ether was added to interact with 50% of K^(+) cations, weak clustering was observed: the clustering was slightly stronger than that of a 50% neutralized ionomer. From this result, it was speculated that in the 50% neutralized sample H^(+) ⇔ K^(+) cation exchange occurs rapidly between -SO₃H and -S0₃K groups in multiplets. which weakens ionic interactions. In the 50% crown ether-added sample, however, -S0₃- group, instead of -S0₃H, is present, and thus no cation exchange is expected to occur.
스타이렌 아이오노머의 기계적인 성질에 미치는 혼합 양이온의 영향
김희석,나연화,이용혁,이법원,유지강,박기주,김준섭 조선대학교 생산기술연구소 1998 生産技術硏究 Vol.20 No.1
The styrene-co-methacrylate ionomers neutralized with Na +, Ba2 +, and mixed cation of both were prepared. The dynamic mechanical properties of two cation-containing ionomers were measured and compared to those of the ionomers neutralized with only one type of cations. We found that in the ionomers with one type of cations the difference in the type of cation does not change the glass transition temperatures. It was found, however, that the cluster Tg of the mixed cation ionomer is lower than that of the single cation ionomers. Thus it was postulated that in the two-cation system the two cations in a solution have sufficient dynamics to form new type of multiplet containing both cations, which may be slightly bigger than that found in the single cation multiplet. The mechanical properties also imply that the strength of ion interactions in the multiplets of the two cation ionomer is thought to be weaker than that of the one cation ionomers. These two effects are believed to contribute the lower in the cluster glass transition of mixed cation system.
A Simple Product Code for Constant-Amplitude Biorthogonal Multicode Modulation
HONG, Dae-Ki,OH, Hyun-Seo,KANG, Bub-Joo The Institute of Electronics, Information and Comm 2009 IEICE TRANSACTIONS ON COMMUNICATIONS - Vol.92 No.4
<P>In this letter, a simple product code is proposed for constant-amplitude biorthogonal multicode (CABM) modulation. In CABM modulation, vertical redundant bits are used for constant amplitude coding. The proposed product code can be constructed by using additional horizontal redundant bits. The hardware complexity of the encoder and decoder pair is very low. Simulation results show that the bit error rate performance of the system with the proposed coding scheme is improved as compared with conventional CABM demodulation.</P>
중등학교 에너지 보존 실험의 검증 및 새로운 실험 방법의 고안
서종식,기대연,이상법 慶北大學校 師範大學 科學敎育硏究所 1999 科學敎育硏究誌 Vol.23 No.-
We examined experiments for kinetic energy conservation in the high school textbook of Physics I and Physics II for the 6th National Science Curriculum and designed a new kit which enables to reduce experimental errors. Most experiments in the existing textbooks deal with the energy conservation for gravitational potential energy transforming to kinetic energy of the same object. We carried out the most commonly used two experiments and found that the experimental errors exceed more than 10~20 percent if carried out without carefulness. This may possibly make students suspect the mechanical energy conservation law. Our new kit, on the other hand, exhibits that the mechanical energy conserves with an error of less than 6% even in the process of transferring the elastic potential energy of one object to the kinetic energy of an another object.
홍대기,강법주,Hong, Dae-Ki,Kang, Bub-Joo 한국정보통신학회 2010 한국정보통신학회논문지 Vol.14 No.10
차량 간 통신을 위한 직교 주파수 분할 다중화 (OFDM: Orthogonal Frequency Division Multiplexing)기반 WAVE (Wireless Access for Vehicular Environment) 시스템의 물리계층 표준은 기존에 정지환경을 기반으로 표준화된 IEEE802.11a 무선랜 (WLAN: Wireless Local Area Network)의 물리계층 표준을 따르는 것으로 되어 있다. 따라서 이동환경에 기반한 WAVE 시스템에서 단순한 등화방식을 적용할 경우 빠른 페이딩의 영향으로 인하여 프레임 초기 채널특성과 말기 채널특성의 변화가 초래되어 시스템의 수신 성능이 저하되게 되고, 특히 고차 변조방식에서는 더욱 문제가 된다. 따라서 본 논문에서는 WAVE 시스템의 64-직교진폭변조 (QAM: Quadrature Amplitude Modulation)과 같은 고차 변조에서 채널 등화성능을 향상시키는 방식에 대해 연구하였다. 훈련 심볼을 이용하는 기존의 채널추정방식을 기반으로 하되 WAVE 채널처럼 빠르게 변화하는 채널특성을 추적하기 위해 일정한 주기 마다 미드엠블을 삽입하는 전송구조를 제안하였다. 또한 미드엠블 사이의 심벌들의 채널 변화는 다양한 보간법을 적용한 등화 알고리듬을 제안하였다. A Wireless Access for Vehicular Environment (WAVE) system based on Orthogonal Frequency Division Multiplexing (OFDM) is made for vehicle to vehicle wireless communications. The physical layer standard of the WAVE system is very similar to that of the IEEE802.11a wireless local area network (WLAN). Therefore, the performance of the WAVE system is degraded by continual channel variation in the WAVE multipath fading channels after starting initial channel estimation. In this paper, we research the performance improvement of equalization in 64 Quadrature Amplitude Modulation (QAM) transmission in WAVE environment. The proposed algorithms use the training sequence and the midamble sequence which is used for fast channel variation such as WAVE environments. Additionally, various interpolation methods are also used for the channel tracking.
움직임 예측을 이용한 움직임 벡터의 고속 추정 알고리즘
김덕규,송홍성,이법기,최정현 경북대학교 전자기술연구소 1994 電子技術硏究誌 Vol.15 No.2
In video coding, a full search method using BMA(block matching algorithm) is widely used to find the motion vector. In this method, the accuracy of the motion vector and the computation burden depend on the size of search window. Previously proposed fast algorithms have reduced the computation complexity by limiting the number of searched locations. Sometimes, this exerts a bad influence on the accuracy of estimated motion vectors, since they can be trapped in the minimum error. In this paper, therefore, we propose a new advanced algorithm of estimating the motion vectors. We estimate the motion vector in motion compensated search area by predicted motion vector. When we find the predicted motion vector, the motion of camera and objects in the previous frame and the correlation in moving objects in the current frame are considered. In spite of small search area, this method improves the accuracy of motion vector and reduces the computation burden.
불균형 이진 트리를 이용한 DCT 기반 벡터 양자화 코드북 설계
이경환,김덕규,이법기,최정현,정태연 경북대학교 전자기술연구소 1997 電子技術硏究誌 Vol.18 No.1
The performance of VQ mostly depends on codebook design method. LBG algorithm is a well known codebook design method. But it is dorminated by initial codebook and has a long computation time. The method of DCT-based design using binary tree was proposed for reducing computation time. However, degradations appear in the edge region of reconstructed image since the blocks of shade region are frequently selected for codevector. In this paper, we propose DCT-based vector quantization codebook design using unbalanced binary tree. As node prunings of shade region are constrained, the number of edge codevector is increased. From simulation results, this method sincerely reconstructs edge region with higher PSNR.